Electrohydraulic metal-forming machine

ABSTRACT

An electrohydraulic metal-forming machine which is capable of simultaneously forming a plurality of sheet-metal or tubular workpieces into the same or different shapes or configurations by electric discharge. The machine comprises a discharge chamber to be filled with a liquid and a pair of electrodes having a gap disposed in the discharge chamber. A plurality of dies of the same or different shapes or configurations are arranged either radially about the discharge chamber in liquid communicating relation thereto or in such a manner that the working surfaces of the dies constitute part of the inner surface of the discharge chamber. A workpiece is put in or applied against each of the dies so that electric discharge causes an impulsive pressure to be generated in the liquid to deform all the workpieces simultaneously to conform to the shape or shapes of the dies.

United States Patent 1 1 3,631,700

[72] Inventor Mitsuo Kosaka FOREIGN PATENTS v 451,834 10/1948 Canada72/56 [2 1 pp 848,286 l,056,343 1/1967 Great Britain 72/56 [2 Filed d-Z13 6,616 6/1962 Japan 72/56 Fi 225$; $368211.- Seisakuaho Ltd. i yExaminer-Richard Kyoto Japan AnorneyFidelman, Wolffe & Leitner [32]Priority Aug. 10, 1968 l Japan [3 '1 43/568 ABSTRACT: Anelectrohydraulic metal-forming machine which is capable ofsimultaneously forming a plurality of [54] ELECTROHYDRAULICMETAL-FORMING sheet-metal or tubular workpieces into the same ordifferent MACHINE shapes or configurations by electric discharge. Themachine 4 Claims, 8 Drawing Figs. comprises a discharge chamber to befilled with a liquid and a [52] U 8 CI 72256 pair of electrodes having agap disposed in the discharge [5]] In. .Cl Bzld 26/12 chamber. pluralityof dies of the same or different Shapes or [50] Fieid 7256,configurations are arranged either radially about the discharge 28/421chamber in liquid communicating relation thereto or in such a mannerthat the working surfaces of the dies constitute part of [56] m- Citedthe inner surface of the discharge chamber. A workpiece is put in or appied against eac of the dies so that eectric UNITED TATES PATENTSdischarge causes an impulsive pressure to be generated in the 30444307/1962 ze'gler 72/56 liquid to deform all the workpieces simultaneouslyto conform 3,096,576 7/1963 Par lla 72/56 to the shape or Shapes ofthedies 3,222,902 12/1965 Bre cha et al. 72/56 3,338,080 8/1967 Golden72/56 i 24 9 1 55 IE PATENTEUJAN 41972 3631700 sum 1 OF 2ELECTROHYDRAULIC METAL-FORMING MACHINE This invention relates to anelectrohydraulic metal-forming machine for forming sheet-metal ortubular workpieces into desired shapes or configurations.

In conventional electrohydraulic metal-forming machines which deal withsheet-metal workpieces, the arrangement is generally such that a sheetof metal to be formed is applied to the working surface of a die, whichis placed upside down or sideways toward an electric discharge chamberfilled with a liquid, so that the impulsive pressure generated in theliquid by discharge is utilized to deform the sheet into the shape orconfiguration as defined by the die. With such conventional machines,however, a single shot of electric discharge can produce only a singleproduct. If the desired final shape is complicated, the forming processmust be carried out in several steps to gradually approach the finalshape, because if the process were carried out by a single shot, theimpulsive pressure would be so concentrated on particular points of theworkpiece that it would suffer an abnormal internal stress and beruptured or broken down. For mass production of such parts ofcomplicated shapes, therefore, there must be provided as many separatemachines having differently shaped dies as there are steps of theforming process, each of the machines taking care of only one of thesteps, with a resulting increase in the cost of equipment and personnelexpenditure.

In conventional electrohydraulic metal-forming machines which deal withtubular workpieces, the arrangement is generally such that a pair ofelectrodes are inserted into the opposite openings of a tubularworkpiece. This arrangement, however, has serious defects such asfollows: First, one of the electrodes requires up-and-down movement andthe gap therebetween, readjustment upon every feeding and unloading of aworkpiece into and out of the machine, and with a single shot ofdischarge it is possible to obtain only a single product. This iscertainly time consuming and quite inefficient. Secondly, the size ofthe electrodes is restricted by the size of the tubular workpiece. Inthe case of a thin tube, for example, the electrodes must becorrespondingly small and thin, with a resulting decrease in theirmechanical strength and shortening of their life. Moreover, the spacebetween each electrode and the inner surface of the tubular workpiecebecomes narrow. This will cause damage to the inner surface of theworkpiece due to the electric discharge between the electrodes and theworkpiece instead of between the two electrodes alone as in normaldischarge. Also, because of the narrow space between the electrodes andthe inner surface of the tube, only a small quantity of liquid can fillthe space, with a resulting pressure drop in the liquid as it goes awayfrom near the electrode tips. This will cause partial bulging of thetube adjacent the electrode tips only. and the longer is the tube, thegreater will be this tendency ofpartial bulging.

The primary object of the invention is therefore to provide anelectrohydraulic metal-forming machine which is completely free of theabove and other defects of the conventional types.

Another object of the invention is to provide an electrohydraulicmetal-forming machine which is capable of simultaneously forming aplurality of workpieces into the same desired single shapes orconfiguration.

Another object of the invention is to provide an electrohydraulicmetal-forming machine which is capable of simultaneously forming aplurality of workpieces into different shapes or configurations.

In one embodiment of the invention, the machine comprises a dischargechamber adapted to be filled with a suitable liquid, a pair ofelectrodes having a gap disposed in said chamber, a plurality of diesarranged radially about said discharge chamber in liquid communicatingrelation thereto and comprising two separable die sections adapted toenclose a workpiece therein so that the workpiece may contact the liquidat its one surface and faces the die at its opposite surface, and meansfor supplying electric energy to said electrodes to cause a sparkdischarge to occur between said electrodes.

In another embodiment of the invention, the machine comprises adischarge chamber adapted to be filled with a suitable liquid, a pair ofelectrodes having a gap disposed in said discharge chamber, a pluralityof movable dies the working surfaces of which constitute at least partof the inner surface of said chamber and are adapted to receive aworkpiece thereon so that said workpiece may contact said liquid at itsone surface and is supplied at its opposite surface against the workingsurface of each said die, and means for supplying electric energy tosaid electrodes to cause a spark discharge to occur between saidelectrode.

The invention will be made clear by the following description withreference to the accompanying drawings in which:

FIG. I is a schematic elevational view, in vertical section, of oneembodiment of the invention;

FIG. 2 is an elevational view, partly in vertical section, of a finishedproduct obtained by the operation of the machine of FIG. 1.

FIG. 3 is a view similar to FIG. 1, but showing another embodiment ofthe invention;

FIG. 4 is a transverse section taken along the line AA of FIG. 3;

FIG. 5 is an elevational view, partly vertical section, of a finishedproduct obtained by the operation of the machine of FIGS. 3 and 4;

FIG. 6 is a view similar to FIGS. 1 and 3, but showing a thirdembodiment of the invention;

FIG. 7 is a transverse section taken along the line BB of FIG. 6; and

FIG. 8 is a perspective view of a finished product obtained by theoperation of the machine of FIGS. 6 and 7.

Referring to FIG. 1, there is shown a housing 11 which defines thelateral sides of a discharge chamber 12 while leaving the top and bottomsides thereof open. The housing 11 is rigidly supported by a machineframe 13. A pair of electrodes 14 and 14' are inserted through theopposite sidewalls of the housing into the discharge chamber 12 so thatthey face each other across a gap 15. To the electrodes there isconnected an energizing circuit 16 including a switch 17 and a condenser18 charged from a suitable source through a transformer 19 and arectifier 20.

A pair of upper and lower dies 21 and 22 are fixed to a pair of dieplates 23 and 24, respectively, each of which is in turn fixed to adriving rod 25, 26 of a suitable oil-pressure-operated clamping device,not shown. Thus, the dies 21 and 22 are movable relative to the housing11 so as to close and open the discharge chamber 12. When the diestightly close the chamber with their respective working surfaces facinginwardly toward the chamber, a suitable liquid 27 is introduced througha passage 33 to fill the discharge chamber 12, so that an impulsivepressure may be generated in the liquid in the manner to be describedlater. The dies 21 and 22 have die cavities 28 and 29 formed on theirrespective working surfaces. The shapes of the dies are different fromeach other and those required at different successive steps of a desiredforming process. That is, the shape of the upper die cavity 28 is thatinto which a workpiece is first shaped at the first step of the formingprocess and the shape of the lower die cavity 29 is that into which thatworkpiece that is through the first step is shaped at the next step toattain the required final shape. The lower die cavity 29 is providedwith a central projection 29 corresponding to the upper die cavity 28. Asealing member 30 tightly seals between the dies 21, 22 and the housing11 against any leakage of the liquid 27 from the chamber 12.

In operation, a workpiece 31a in the form of sheet metal is held betweenthe upper die 21 clamped into the chamber closing position as shown inFIG. 1 and the upper shoulder 32 of the housing 11 so that one surfaceof the workpiece 30 is applied against the working surface of the upperdie 21, and with the lower die 22 having been clamped into the chamberclosing position, liquid 27 is introduced into the discharge chamber,whereupon the opposite surface of the workpiece is in contact with theliquid filing the discharge chamber. As the liquid fills the chamber,the air therein is pushed out therefrom through a passage 33'. Under thecondition, when the switch 17 is closed, a discharge takes place acrossthe gap between the electrodes 14 and 14' and causes an impulsivepressure to be generated in the liquid 27. This pressure deforms theworkpiece 31a to conform to the shape or configuration of the workingsurface of the upper die 21. That is, the portion of the workpiece whichcorresponds to the upper die cavity 28 is depressed thereinto to conformto the shape thereof, so that a depression or projection 31' is formedin the workpiece. Evacuation of the die cavity 28 through a passage 34prevents the air in the cavity from restricting the proper deformationof the sheet metal 33.

When the first shot of discharge has been completed, the liquid 27 iswithdrawn from inside the discharge chamber through the passage 33, andthe dies 21 and 22 are moved away from the housing 11 to remove theworkpiece from the upper die 21. Then, this workpiece 31a is heldbetween the lower die 22 clamped into place and the lower shoulder 32'of the housing 11, and a new workpiece 31b is held between the upper dieclamped into place and the upper shoulder 32 of the housing 11. Afterthat, the liquid is again introduced into the discharge chamber to fillthe same, and a discharge is again caused to occur in the mannerpreviously described. As a result of this second shot of discharge, theupper workpiece 31b is deformed just in the above-mentioned manner, andthe lower workpiece 31a is deformed to conform to the lower die cavity29, with the projection 29' thereof fitting into the depression 31'already formed in the workpiece 31a at the preceding step of the formingprocess. A pair of passages 34 are provided to evacuate the lower cavity29 for the same purpose of the above-mentioned relief passage 34.

After the second shot of discharge, the liquid in the chamber iswithdrawn and the two dies are removed from the housing 11. The finishedarticle taken out of the lower die is shown in FIG. 2.

The structure of FIG. 1 is designed to perform two different shapes of aforming process simultaneously, that is, by a single shot of electricdischarge. If the forming process requires more than two steps, thecorresponding number of dies must be provided. FIGS. 3 and 4 show anarrangement suitable for performing the four different steps of aforming precess at the same time.

A housing 35 supported by a base 36 defines a discharge chamber 37therein and has four windows 35a, 35b, 35c and 35d. A pair of electrodes38 and 38' are inserted through the top and bottom walls 35' and 35" ofthe housing 35 into the chamber 37 so that they are juxtaposed across agap 39. To the electrodes there is connected an energizing circuit 40similar to the circuit 16 in FIG. 1 including a switch 41 and acondenser 42 charged from a suitable source through a transformer 43 anda rectifier 44.

Four different dies 45, 46, 47 and 48 carried by die plates 49, 50, 51and 52, respectively, are movable relative to the housing 35 to open andclose the windows 35a, 35b, 35c and 35d of the housing 35 by means ofrods 53, 54, 55 and 56, respectively, each of which is driven by asuitable oil-pressureoperatcd clamping device, not shown.

When the four dies tightly close the discharge chamber 37 with theirrespective working surfaces facing inwardly toward the chamber, suitableliquid 57 is introduced into the chamber through a passage 64 to fillthe chamber. The dies 45-48 have formed on their respective workingsurfaces die cavities 58, 59, 60 and 61, the shapes or configurations ofwhich are those required at the four different steps of a requiredforming process. Sealing members 62 tightly seal between the housingwalls and surfaces of the workpieces applied against the dies, so thatthe liquid in the chamber 37 may not enter the die cavities.

In operation, a workpiece 63a in the form of a sheet of metal is appliedagainst the die 45, and after the first shot of discharge, it is removedfrom the first die 45, with a depression 63 formed thereon, onto thesecond die 46. At the same time,

a new sheet of metal 63b is held against the first die 45, and after thesecond shot of discharge, the first workpiece 63a has a configuration63" formed thereon and is removed from the second die 46 onto the thirddie 47. At the same time the second workpiece 63b is transferred fromthe first die 45 onto the second 46, with a new workpiece 630 beingplaced on the first die 45. Then after the third shot of discharge, thefirst workpiece 63a has a configuration 63" formed thereon and istransferred from the third die 47 onto the fourth die 48. At the sametime, the second and third workpieces 63b and 63c are transferred fromthe second and first dies 46 and 45 onto the third and second dies 47and 46, respectively, and a fourth workpiece 63d is placed on the firstdie 45. Then, after the fourth shot of discharge, the first workpiece63a has been formed into the final desired shape as shown in FIG. 5. Itwill be easily seen that from the next shot of discharge every singleshot of discharge can effect simultaneous deformation of four workpiecesinto four different shapes. Relief passages 85 are provided forevacuation of the die cavities just as in the arrangement of FIG. 1.

FIGS. 6 and 8 show a third embodiment of the invention designed forforming a plurality of tubular workpieces into the same shapesimultaneously. There are shown a pair of upper and lower die sections65 and 66. The lower die sections 66 is rigidly supported by a base 67,while the upper die section 65 is fixed to a die plate 68 and verticallymovable relative to the lower die section 66 by means of rods 69 drivenby a suitable oil-pressure-operated clamping device, not shown. When puttogether, the two die sections define a central discharge chamber 70 andfour die cavities 71 of the same shape or configuration. The four diesare arranged radially about the discharge chamber 70 in liquidcommunicating relation thereto. A pair of electrodes 72 and 72' areinserted through the upper and lower die sections into the dischargechamber 70 so as to face each other across a gap 74. The electrodes areconnected to an energizing circuit 75 including a switch 76 and acondenser 77 charged from a suitable source through a transformer 78 anda rectifier 79.

In operation, a workpiece 80 in the form of a tube is placed in each ofthe four dies, with a stopper 81 fitted into the outer end opening ofthe tube. A suitable liquid 82 is introduced into the chamber 70 througha passage 83 in the lower die section to fill the chamber and also thefour tubular workpieces 80. As the liquid fills the chamber and theworkpieces 80, the air therein is pushed out through a relief passage83' in the upper die section. Sealing rings 84 prevent the liquid fromentering between the inner surface of each die and the outer surface ofthe tube. Relief passages 86 are provided for the same purpose as in theprevious arrangements.

When the switch 76 is closed, an electric discharge taking place betweenthe electrodes causes an impulsive pressure to be generated in theliquid 82. This pressure deforms the tabular workpieces to conform tothe same shape of the four dies. The final shape of the workpieces isshown in FIG. 8. It is seen that the machine of FIGS. 6 and 7 is capableof dealing with four workpieces at the same time. Needless to say, thenumber of dies provided may be increased or decreased as occasionsdemand. Such modified forms with more or less dies will be so apparentto those who have read the specification that no illustration orexplanation will be necessary.

In the illustrated embodiments of FIGS. 1, 3 and 4, the shapes of thedies are mutually related, that is, those shapes into which theworkpiece is formed at different succeeding steps of a required formingprocess directed to a single final shape. If desired, the dies may havedifferent independent shapes having no mutual relation. Also in FIGS. 6and 7 the dies are of the same shape, but they may have differentshapes, whether mutually related or not.

If the workpiece is so thick or of so rigid a material that a singleshot of discharge may not sufficiently deform it, a plurality of shotsmay be conducted to deform the workpiece to the shape of the die.

in accordance with the invention, as the number of workpieces to beformed increases, the amount of discharge energy required of courseincreases, but not proportionally, as experiments conducted by thepresent inventor have disclosed. For example, the amount of energyrequired for formation of four workpieces at the same time in accordancewith the invention is about one and a half times the amount of energyrequired for formation of one workpiece. This means that the machine ofthe invention has a very higher working efficiency than the conventionaltypes of machines, and that the greater is the number of workpieces tobe formed simultaneously, the higher the efficiency becomes.

What I claim is:

1. An electrohydraulic metal-forming machine comprising: a centraldischarge chamber adapted to be filled with a liquid, a plurality ofdies arranged radially about said chamber in liquid communicatingrelation thereto and comprising two separable die sections adapted toform a plurality of tubular chambers radially extending from saiddischarge chamber, each said tubular chamber enclosing a tubularworkpiece therein so that said workpiece may contact said liquid at itsone surface and faces said die at its opposite surface, a pair ofelectrodes having a gap disposed in said discharge chamber and outsidesaid tubular chambers, and means for supplying electric energy to saidelectrodes to cause a spark discharge to occur between said electrodes.

2. The machine of claim 1, wherein said dies have the same shape.

3. The machine of claim 1, wherein said dies have different shapes.

4. The machine of claim 3, wherein said different shapes are those intowhich each said workpiece is formed at different succeeding steps of aforming process.

1. An electrohydraulic metal-forming machine comprising: a centraldischarge chamber adapted to be filled with a liquid, a plurality ofdies arranged radially about said chamber in liquid communicatingrelation thereto and comprising two separable die sections adapted toform a plurality of tubular chambers radially extending from saiddischarge chamber, each said tubular chamber enclosing a tubularworkpiece therein so that said workpiece may contact said liquid at itsone surface and faces said die at its opposite surface, a pair ofelectrodes having a gap disposed in said discharge chamber and outsidesaid tubular chambers, and means for supplying electric energy to saidelectrodes to cause a spark discharge to occur between said electrodes.2. The machine of claim 1, wherein said dies have the same shape.
 3. Themachine of claim 1, wherein said dies have different shapes.
 4. Themachine of claim 3, wherein said different shapes are those into whicheach said workpiece is formed at different succeeding steps of a formingprocess.